1. Field of the Invention
The present invention relates to a recording tape cartridge which rotatably accommodates a reel onto which recording tape, such as a magnetic tape or the like, is wound.
2. Description of the Related Art
Recording tapes such as magnetic tapes and the like are used as external recording media for computers and the like. “One-reel” recording tape cartridges, which rotatably accommodate a single reel around which a recording tape is wound, require little space when stored and can record large amounts of information, and are employed as such recording tapes.
Such a recording tape cartridge is equipped with a brake mechanism such that the reel does not rotate in the case at times of non-use of the recording tape cartridge (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 63-251983). JP-A No. 63-251983 discloses a structure in which a reel hub, which is formed in a cylindrical tube shape with a base, and which structures an axially central portion of a reel is provided with an engaging gear formed in an annular form at a bottom face of the reel hub, and a disk-shaped locking which member is provided with a braking gear which is meshable with the engaging gear being inserted in the reel hub. The locking member is supported to be non-rotatable with respect to the case but slidable in an axial direction of the reel. The braking gear of the locking member can mesh with the engaging gear of the reel by urging force of a compression coil spring which is provided between the locking member and the case. In this state, the reel is pressed against a bottom plate of the case by the urging force of the compression coil spring, and the braking gear is meshed with the engaging gear by the urging force. Thus, rotation of the reel relative to the case is locked.
In this structure, a through-hole is formed in a base portion of the reel hub. A release portion of a drive device advances in through this through-hole and pushes up the locking member against the urging force of the compression coil spring. Accordingly, the state of meshing of the braking gear with the engaging gear is released. As a result, rotation of the reel relative to the case is enabled (permitted). The release portion of the drive device is provided at a rotating shaft, together with a driving gear which meshes with a reel gear formed at an end face of the reel hub. The release portion pushes up the locking member in accordance with an operation of meshing the driving gear with the reel gear. As a result, when the rotating shaft drives to rotate the reel, the locking member, which is non-rotatable with respect to the case, and the release portion, which rotates integrally with the rotating shaft, slidingly contact one another while being pushed against each other by the urging force of the compression coil spring. Thus, in order to reduce rotational resistance which is generated in accordance with this sliding contact, the locking member and the release portion are both formed by resin materials.
Further, structures have been devised in which a release member, between a locking member and a base portion of a reel hub, rotates integrally with the reel (see, for example, the specification of Japanese Patent No. 3,187,022). Specifically, the release member is pushed by a release portion of a drive device and, together with the locking member, is pushed up against urging force of a compression coil spring. Thus, the locking member is pushed up to the release portion via the release member, and releases a locked state of the reel. Hence, with this structure, when the reel is driven to rotate, the release member rotates integrally with the reel. Therefore, rather than the release portion slidingly contacting the release member, the release member and the locking member slidingly contact one another.
However, structures are known in which locking members do not slide-contact other components at times of driving for rotation of a reel (see, for example, JP-A No. 11-25648). In such a structure, an engaging gear is formed at an outer peripheral portion of a flange of the reel. Two locking members, which are supported to be rotatable in the case and are urged in a direction of meshing with an engaging gear, mesh with the engaging gear and hence lock rotation of the reel. When such a recording tape cartridge is loaded at a drive device, the locking members are pushed by respective engaging portions of the drive device and are rotated against the urging force. Thus, the meshing of the locking members with the engaging gear is released and rotation of the reel is enabled. These release portions are provided respectively separately from a rotating shaft, and push the locking members in accordance with loading of the recording tape cartridge (the case) into the drive device or an operation of lowering the cartridge. Further, at this structure, a compression coil spring for pushing the reel against the case and/or the rotating shaft is coupled with the reel via a bearing, such that relative rotation of the compression coil spring with respect to the reel is absorbed by the bearing.
However, with the structures described in JP-A No. 63-251983 and the specification of Japanese Patent No. 3,187,022, the urging force of the compression coil spring acts as a drag at a region of sliding contact between the locking member and the release member or the release portion of the drive device. Therefore, if, in correspondence with an increase in recording capacity, the recording tape is lengthened and a rotation speed of the reel is increased and/or a duration of continuous driving is lengthened, the occurrence of abrasion at the sliding contact region will be a matter of concern. Further, in the structure described in JP-A No. 11-25648, an urging mechanism which urges the locking member in the direction of meshing with the engaging gear is a separate component from a compression coil spring which urges the reel toward a bottom plate of the case. Therefore, relative rotation of the reel and the compression coil spring cannot be absorbed by the locking member rotating relative to the reel. Accordingly, it is necessary to absorb such relative rotation with a costly bearing.
Further, the recording tape cartridges relating to the structures described above are structures in which, at times of non-use of the recording tape, the reel is pressed against the bottom plate of the case by the urging force of the compression coil spring. Therefore, it is not possible to obstruct (lock) vertical movement of the reel within the case when a force opposing the urging force of the compression coil spring acts thereon. Consequently, if, for example, a portion of the reel at which the reel gear is formed and which is exposed from the case (an outer face of the base portion of the reel hub) is pushed against or is subjected to an impact due to falling, the reel moves very loosely in the case, which leads to damaging the recording tape, whose one end portion is retained in the case by means of a leader member.
Thus, consequent to the provision in conventional recording tape cartridges of compression coil springs which urge reels relative to cases directly or via locking members, various problems have occurred.